Different diagram types/shapes support different connectors (lines) types, and the connector type can be selected from the drop-down selection on the contextual toolbar. For instance, if you're using the UML diagram types, ER diagram types, or Network diagrams you'll be able to access different connector types.
UML Use Case Diagram
Entity Relationship Diagram
UML Class Diagram
Select a connector style
The default connector style for each diagram type is automatically set up to enable faster visualization. But you can always change the style from the contextual toolbar to suit your requirements.
Select an arrow style
Simply change the arrow direction with a single click. This is helpful if you're drawing a complex diagram.